The automatic dishwasher, or ADW, has become a part of today's society. More and more households own one and therefore, the products that are used with them are evolving quickly. First there was a need to add a main wash cleaning composition in powder form, rinse aid and salt for a wash program. Next, the main wash cleaning composition evolved from loose powder into a compressed powder tablet to simplify dosing the right amount powder. Additional rinse aids and salt were still needed; however, it did not take long before all-in-one tablet solutions were available on the market.
Despite the fact that most of the practical aspects of cleaning results have been improved, there are still performance issues with the ADW. For instance, consumers have accepted that rinsing, and soaking dishes prior to loading dishes in the ADW is needed to make sure the dishwasher can completely clean the dishes. In addition, spotted glasses and the need for towel drying dishes are almost accepted flaws of the automatic dishwasher. Therefore, there is a need to find a solution that eliminates these compensatory behaviors and enables a consumer to get the most out of the automatic dishwasher's performance capabilities.
Research has shown that the main reason these problems exist is that all cleaning compositions in the tablet are released at the same time. Some cleaning compositions counteract or are not fully compatible with each other, leaving the full potential cleaning performance unmet. Thus, a dispensing device is desired that can sequentially release cleaning compositions at defined times during the wash program that can increase the cleaning performance of the automatic dishwasher.
Wash programs for ADWs can contain five different cycles: pre-wash, main wash, rinse cycle, dry cycle and purge cycle. The different wash cycles occur in the order of pre-wash, main wash, and rinse cycle. The water is typically refreshed between each wash cycle (e.g. Pre-wash or Main wash cycle). Not all wash programs contain all cycles and it is possible that some cycles could occur twice or even three times. Thus, a dispensing device for releasing cleaning agents in an automatic dishwasher needs to be capable of sensing the wash cycles. Wash cycles may be distinguished by water temperature; however, determining which cycles are heated and which cycles are not depends on the dishwasher brand and model. In general the main wash and final rinse cycles are heated for improved cleaning performance; however, prewash cycles can be heated or cold.
An overview wash cycle programs based on several machines currently in the market illustrates the diversity of ADW wash cycles.
Pre-Wash
    Occur # times in wash program: not at all, 1-2 or even 3 times Heated: depends on wash cycle    Temperature range: 5-50° C.    Duration: 4-25 minutesMain Wash    Occur # times in wash program: Once/always in wash program Heated: Yes, always    Temperature range: 37-75° C.    Duration: 16-85 minutesRinse Cycle    Occur # times in wash program: 1-2 or 3 times    Heated: depends on wash cycle    Temperature range: 5-75° C.    Duration: 3-47 minutesDry Cycle    Occur # times in wash program: Once in wash program    Heated: depends on ADW model    Temperature range: 72° C. to room temperature (20° C.)    Duration: till user opens ADW door
As shown, the temperature and duration values between pre-wash and main wash cycles often overlap making it difficult to distinguish between these cycles.
A majority of dishwashers today feature a minimum of three wash programs; however, models exist with up to fifteen wash programs. The different wash programs having different cycle times and temperature profiles emphasizes the significance of correctly sensing the wash program and corresponding wash cycles for the sequential release of cleaning agents. It has been determined that ultimate cleaning performance can be achieved by releasing one cleaning composition during the pre-wash cycle, two preferably three cleaning compositions during the main wash cycle and one cleaning composition during the rinse cycle.
The challenge for wash program sensing is determining what parameters to measure in order to clearly distinguish between the wash cycles. For instance, wash cycle parameters such as temperature, water flow and cycle duration (time) can be measured and used to automatically trigger the release of cleaning agents during the wash program. Other parameters include pH value, conductivity, turbidity and motion.
Temperature
With temperature you can follow the progress of heated and cold cycles; however, the warm water inlet in North America vs. the cold inlet in Europe as well as overlapping temperature profiles of different cycles can present a problem.
Time (Duration)
Very diverse time values exist for the different wash programs. For instance, pre-washes range from single prewash cycles of 7 minute duration to double prewash cycles with each prewash cycle having duration of 3 to 5 minutes. Main wash cycles can vary from 30 minutes to 75 minutes.
Water Flow
Water flow sensors can be used to detect water flow similar to sensors used to detect water droplets on windshields of cars having automatic wipers.
pH Value
The pH value of the water will change when cleaning compositions are released. It is possible to use a pH sensor to recognize cycle transitions for instance if prewash cycle has a high pH level when prewash cleaning compositions are released, there will be a big drop in the pH level once the water is drained and replenished for the main wash cycle. This can indicate a cycle transition.
Conductivity
Conductivity works similar to the pH level option. The conductivity value depends on which amount, and of which chemicals are already released. However, it will not distinguish a pre-wash cycle from a main wash cycle.
Turbidity
Turbidity is already used in modern ADW's for sensing how dirty the dishes are. This can be used to determine cycle transition when water is refreshed between cycles. However, it may be easier to detect water flow instead.
Accelerometer (Motion Sensor)
The only parts of an automatic dishwasher that will move during the wash program are the spray arms. The rotation could be sensed with an accelerometer however this requires attaching a sensor to the spray arms. Since rotation of the spray arms is typically controlled by water flow, the added weight of a sensor could affect performance.
Another option is to sense the movement in front of the water intake with a motion sensor, so the sensor will know when the tub is filled (start of wash program and during cycle changes). However, the placement of the sensor will be essential and not preferred to be left to the consumer. Alternatively, a motion sensor could be connected to the dosing chamber door that opens during the main wash cycle. This approach has similar drawbacks in that it relies on the consumer to close the dosing chamber door even though cleaning composition is not placed inside.
Hall Sensor (Magnetic Field Sensor)
Magnetic fields exist during operation of the dishwasher that are registerable. Such magnetic fields are created by solenoid valves which are mainly used for opening the dosing chamber and for the water intake. However, these are so weak that you would have to place the sensor very close to the source (e.g. 10 cm). In addition, not all ADW's use solenoid valves.
Opening of Dosing Chamber
The dosing chamber containing the ADW cleaning composition always opens in the main wash providing a good indication point. A magnet may be stuck on the dosing chamber and sensed with a hall sensor to determine when it opens indicating the start of the main cycle. However, the device will have to be placed directly in front of the dosing chamber requiring placement by the consumer which is not preferred.
To conclude, most of the sensor options can be effective in detecting cycle transitions, but not so effective distinguishing cycles from one another. As discussed earlier, only the main wash cycle includes opening of the dosing chamber which distinguishes it from a pre-wash or rinse cycle. While a combination of sensors improves the ability to effectively distinguish cycles, the overlapping cycle characteristics across ADW machines makes it difficult to distinguish all cycles. For instance, it is impossible for a sensor system to predict whether a second or third hot rinse cycle will follow a first hot rinse cycle. As a result, it will automatically release all rinse compositions during the first rinse cycle, instead of during the last hot rinse cycle which is preferred. Similarly some wash cycle programs have a longer hot prewash cycle than the main wash cycle of wash cycle programs having zero pre-wash cycles causing the device to mistakenly identify the long pre-wash as a main wash and prematurely release the main wash composition during the prewash cycle.
Therefore, there is a need for a device that can release the right chemistry at the right time inside the automatic dishwasher. However, since a number of different wash programs exist within and across all dishwasher brands, the device must be capable of releasing the right chemistry at the right time consistently across all dishwasher brands and wash programs. Therefore, a dispensing device is desired that includes a wash cycle sensing system to detect wash cycle parameters such as temperature, water flow relative to time which in conjunction with an algorithm can be used to determine the preferred chemistry release points inside the dishwasher during the different phases of the wash cycle. In addition, since the cycle parameters can overlap and fluctuate between wash cycles, a recording function may be implemented to store the sensed cycle data and effectively ‘learn’ the wash cycles used and modify the algorithm in order to adjust the best release points based on the wash cycles chosen by the consumer. The result is a personalized cleaning composition dispensing device tailored to a consumer's dishwasher and corresponding dishwashing behavior that increases the cleaning performance of the dishwasher in such way that the compensatory behaviors are no longer needed.